1. Field of the Invention
The present invention relates to a semiconductor device having a light receiving element.
2. Description of the Related Art
A CMOS image sensor is a semiconductor device, and includes in general, as a light receiving element, a pixel array of one-dimensionally or two-dimensionally arranged light receiving elements in a light receiving portion. Each pixel of the pixel array in the light receiving portion includes a photodetector formed from a photodiode having a PN junction. In each pixel, incident light is absorbed in a semiconductor substrate to generate carriers, and the generated carriers recombine in a depletion layer portion of the photodiode, making a voltage or a current which is obtained as an output. At this time, the incident light is reflected by an upper layer film of the PN junction to cause interference, and hence output fluctuations may occur depending on fluctuations in thickness of the upper layer film, causing a practical problem. Crosstalk due to oblique incidence of the light is also a problem. Further, the carriers generated at places other than a desired PN junction may become a source of a dark current.
As a solution of those problems, there is proposed a method involving shielding light at regions other than a light receiving element region with a metal wiring layer, to thereby suppress the light interference and the generation of the dark current (for example, see Japanese Patent Application Laid-open No. 2010-45280).
However, the light cannot be completely shielded in the portions where the wirings are led out for electrical connection between an internal circuit and a sensor portion. In addition, a void may be formed due to stress migration by the upper layer film when a light-shielding metal width is large, and a short circuit may occur due to hillocks when the interval between the metal wirings is small.